The invention relates to a method for making shaped foam glass bodies.
Shaped foam glass bodies as well as methods for making them are known. The shaped bodies may have the shape of small spheres of plates or differently shaped objects. Spherical foam glass bodies, in particular, are used as insulating agents in the construction industry, but also as floating wicks which absorb oil on water surfaces so as to permit removal of the oil by burning it away. Plate-shaped foam glass bodies can likewise be used as heat and sound insulating materials; they also serve as supports for objects which require heat treatment as well as numerous other purposes.
When producing shaped foam glass bodies, the starting materials, if possible, are those that are inexpensive and available in large quantities. Comminuted waste glass, i.e., for example, comminuted bottles, window panes, wastes from glass factories and the like are particularly suitable. Moreover, it is known to process raw materials existing in nature, such as clays and the like as well as industrial wastes such as ashes or the like. In all cases, the usually finely ground starting material is hydrolyzed by chemical wet treatment, the resulting slip is dried and granulated and the granulate is dried and foamed by heating it to higher temperatures. The necessary expansion agent may be added already to the hydrolysis mixture; it is also known, however, to add the expansion agent to the slip at a later time.
German Patent No. 2,151,232 discloses a process for making a water containing product of mixed silicates for use as a raw material for the production of foam glass in plate or granulate form. To produce the raw product, chunky alkali silicate produced by melting (so-called piece glass) is filled together with water and powdered and/or fibrous alkali soluble oxidic and/or silicate starting material into a roller autoclave and is heated by introducing steam. The weight ratio of the alkali silicate to the glass or the like to be hydrolized is 1:0.02 to 0.8. During the introduction of the steam, the autoclave content is heated and brought to elevated pressures of 1 to 5 atmospheres gauge. This causes the chunky alkali silicate to slowly go into solution and, because of the waterglass solution in statu nascendi, the oxidic and/or silicate substances are dissolved, i.e. hydrolized. The hydrolysis process takes several hours, during which the mass must always remain flowable so as to be able to be moved in the roller autoclave. The resulting slip is then dried and the resulting powdery product is processed further in a known manner into shaped foam glass bodies.